These studies are directed at a better understanding of 3 aspects of neural control of the circulation: 1. Regulation of cerebral blood flow; 2. Control of blood flow through vasa vasorum; 3. Effects of hypoxemia. Specific goals for this year were: 1. Examination of effects of sympathetic nerves on cerebral vessels during normotension and severe hypertension. 2. Determination of constrictor and dilator properties of vasa vasorum in the aortic media. 3. Effects of dopamine on ventilation in man. Research goals for the coming year are to answer these questions: 1. Is there an interaction between adrenergic and cholinergic nerves to cerebral vessels? 2. Does occlusion of vasa vasorum in hypertensive dogs produce dissecting aneurysm of the aorta? 3. Is there an interaction between dopaminergic and cholinergic receptors in the carotid body?